Instructions for setting up environment without colab are slightly outdated

[mwaskom]

(Porting discussion from TA training)

https://github.com/NeuromatchAcademy/precourse/blob/master/getting-ready-python/02-getting-ready-python-without-colab.md#how-to-get-started-on-python-tutorials-without-google-co-lab

The course-content repo defines an environment.yml (and requirements.txt) file, so we can cut the instructions for writing that (the dependencies are also slightly out of date).

[jerlich]

I recently set up my environment like this : conda env create --file=environment.yml